This invention relates to the field of hematopoietic stem cells, specifically to the use of vascular tissue to reconstitute hematopoiesis in a subject.
All the blood cells that circulate in the peripheral blood are derived from primitive mesenchymal cells referred to as hematopoietic stem cells. In the adult, most of these cells are located in the bone marrow. In the marrow of a healthy person, most stem cells are neither dividing nor differentiating. These cells are considered to be in a prolonged intermitotic interval and comprise the reserve stem cell pool that can be induced to divide upon hematopoietic stress.
Hematopoietic stem cells are self-regenerating, and also pluripotent in that they differentiate info several lineages, including lymphoid, myeloid and erythroid lineages. The lymphoid lineage, comprising B-cells and T-cells, provides for the production of antibodies, regulation of the cellular immune system, detection of foreign agents in the blood, detection of cells foreign to the host and the like. The myeloid lineage, which includes monocytes, granulocytes, megekaryocytes as well as other cells, monitors for the presence of foreign bodies in the blood stream, provides protection against neoplastic cells, scavenges foreign materials in the blood stream, produces platelets, and the like. The erythroid lineage provides the red blood cells, which act as oxygen carriers. Exposure to growth factors is believed to induce a stem cell to be dedicated to differentiate into a specific lineage.
The stem cell population is known to constitute only a small percentage of the total number of leukocytes in bone marrow. Recently, the mouse stem cell has been obtained in at least highly concentrated, if not a purified form, where fewer than about 30 cells obtained from bone marrow were able to reconstitute all of the lineages of the hematopoietic system of a lethally irradiated mouse. Indeed, one injected cell should be able to reconstitute all of the hematopoietic lineages.
There is a strong interest in identifying sources of hematopoietic stem cells, as possession of these sources will allow for identification of growth factors associated with its self-regeneration. In addition, there may be as yet undiscovered growth factors associated (1) with the early steps of dedication of the stem cell to a particular lineage; (2) the prevention of such dedication; and (3) the negative control of stem cell proliferation. The availability of new sources of stem cells can be extremely useful as a substitute for bone marrow transplantation, as well as in transplantation of other organs currently performed in association with transplantation of bone marrow. In addition, stem cells are important targets for gene therapy, where the inserted genes promote the health of the individual into whom the stem cells are transplanted. Identification of a new source of stem cells thus provides additional means of isolating cells useful in gene therapy. Isolation of a novel hematopoietic stem cell, or a novel intermediate in hematopoiesis, also provides new avenues for treatment of lymphomas and leukemias, as well as other neoplastic conditions, e.g., breast cancer. Model systems to isolate and test stem cells and hematopoiesis also provide a means for testing agents that affect stem cells.
A method is provided for enhancing hematopoiesis. The method includes transplanting at least a therapeutically effective portion of an isolated vascular tissue into a subject, wherein the vascular tissue enhances hematopoiesis.
In one embodiment, a method is provided for detecting agents that affect hematopoiesis. The method includes transplanting a portion of an isolated vascular tissue into a subject, wherein the portion of the isolated vascular tissue is sufficient to enhance hematopoiesis. The vascular tissue is treated with a candidate agent, and hematopoiesis is monitored in the subject. Hematopoiesis in the subject may be compared with hematopoiesis in a control subject, or compared to expected reference values, with reference to hematopoiesis in general or certain cell types (such as leukocytes, for example lymphocytes). A change in hematopoiesis in the subject as compared to the control indicatives that the agent affects hematopoiesis.
In another embodiment, a method is provided for isolating a hematopoietic growth factor. The method includes transplanting a portion of a vascular tissue into a subject, wherein the portion of the vascular tissue promotes hematopoiesis in the subject; and isolating a hematopoietic growth factor from the subject. Another embodiment is the hematopoietic growth factor itself, whether isolated by this approach or directly from the blood vessel itself.
In a further embodiment, a method is provided for isolating a hematopoietic stem cell. The method includes transplanting a portion of a vascular tissue into a subject, and isolating a hematopoietic stem cell from the subject.
A pharmaceutical composition is provided for promoting hematopoiesis that includes a therapeutically effective amount of an isolated vascular tissue in a pharmaceutically acceptable carrier. A method of making a pharmaceutical is also disclosed. The method includes obtaining a portion of a vascular tissue for use in enhancing hematopoiesis.
A kit is disclosed for promoting hematopoiesis. The kit includes a carrier means comprising a container which includes a portion of an isolated vascular tissue in a medium, such as a preservative medium that does not interfere with the hematopoietic activity of the vascular tissue. The use of an isolated blood vessel for hematopoiesis, is also disclosed, and this use can, for example, be disclosed in instructions included with the kit.
A non-human animal model is also disclosed for testing agents that affect hematopoiesis. The model system is a non-human animal deficient for hematopoiesis transplanted with an isolated portion of a vascular tissue, wherein the portion of the vascular tissue is sufficient to promote hematopoiesis. A method for generating the non-human animal model is also disclosed.